This invention relates to the field of integrated circuits and particularly to fixtures for testing high frequency devices.
In the testing of high frequency chip carriers, the efficient transmission of energy from the chip carrier to the measuring instruments is an important design requirement which calls for precise electrical matching of all components. The aim is to produce precise impedance matching at smooth, lossless transitions when waveguides are coupled to the chip carrier being tested and to instruments and other devices in the test set up. Microwave transmission is extremely sensitive to surface discontinuities which cause power losses and induce unwanted reflections. These inefficiencies particularly show up when surfaces join or abut each other. These losses, in addition to reflection losses due to impedance mismatch, are insertion losses and are present at any junction.
Leadless chip carriers have metal pads which are designed to be bonded directly into circuits without the use of leads, hence they are termed "leadless". To test these chip carriers, a socket is needed to hold the carriers and to contact each of their metal pads. Conventional leadless chip carrier sockets use separate metal springs which contact the metal pads on the carrier when it is inserted into the socket. These spring contacts introduce insertion losses and impedance mismatch, and there is a continuing need to provide convenient test sockets which minimizes such inefficiencies.